The present invention relates generally to a portable device and, more specifically, to a portable device having a high-resolution display for viewing still and video images and having multi-media capability.
People that have a portable lifestyle would appreciate instant access to a large amount of information via a portable device, such as a mobile phone, personal data assistant, communicator and the like. While it is a common practice to use a low-resolution liquid-crystal display (LCD) panel to display network information and text messages, it is preferred to use a high-resolution display to browse rich information content of text and images. The high-resolution displays typically have at least SVGA (800xc3x97600 pixels) resolution and are of an active matrix type. They can be used for direct view displays or virtual displays. The virtual displays are known as Near Eye Displays (NED). Direct view displays can be visible simultaneously to several observers, whereas the virtual display is only for one person. Virtual displays consist typically of a microdisplay and imaging optics. They can be monocular or binocular. The perceived image in a virtual display can be larger than the device itself. The usability of the virtual display depends very much on the performance of the microdisplay and optics.
The size of the beam of light emerging from imaging optics towards the eye is called exit pupil. In NED, it is typically of the order of 10 mm in diameter. The ease of the use of a virtual display would be improved significantly if the exit pupil were enlarged. When the exit pupil is large enough, the device can be at a distance from the eye, and the display would not then be NED, but would still be a virtual display. In this context, this operating mode is called Window-mode.
The pixel pitch, which is resolvable to the human eye, determines the necessary size of a high-resolution direct view display. This means, in practice, that the size of the display would be larger than the small portable device itself. In addition to virtual display, projection of an image also provides a method to overcome this dilemma. However, the power consumption of the illumination would be too high for a battery operated portable device, even if the projected image is only about 10 inches in diagonal. It is advantageous and desirable to provide a method that can show high-resolution images in reasonable size. In battery-operated devices, the window or projection mode is desirable. The power consumption in window mode is slightly larger than in NED mode, but is reasonable for a battery operation. The power consumption in projection mode depends on the size of the projected image. Thus, in battery operation the projected image size would be limited. If the projected image is the size of a typical computer monitor or larger, a connection to an external light source is necessary.
The primary objective of the present invention is to use a portable device having a display system, which can work in several display modes, using a microdisplay as an image source and enlarging the image by different optical arrangements corresponding to different display modes.
The first mode of operation is a virtual Near Eye Display (NED), which typically uses a microdisplay as an image source and an imaging optical arrangement to deliver the image to the eye of a viewer.
The second mode is a Near Projection Display (NPD), which uses a near field projection optical arrangement to provide a projected image on a screen at a near distance of 5-25 cm, for example.
The third mode is a Window Mode Display (WMD), where the image appears through a special optical element, which enlarges the exit pupil of the imaging optical arrangement so that the image appearing on the microdisplay is provided as a virtual image to a viewer at a distance.
The fourth mode is Projection Display (PD), whereby the image is projected onto a screen, at a distance of 0.5 m-2.5 m from the device, and the real image appears to be up to 1 m in diagonal, for example.
According to the present invention, an optical engine is used to form an image based on the optical arrangements of each mode of operation of the device. The optical engine consists of an image source, such as a microdisplay device, a light source, one or more lenses for collecting light from the light source for illuminating the image source, other optical elements and one or more lenses which form the imaging optics. A number of different lens arrangements are used to achieve the desired display modes. The internal light source, powered by one or more batteries in the portable device, is used for illumination in the first three modes. For projecting an image at a screen disposed at a distance from the portable device, however, an external light source may be needed. Preferably, the illuminating light from the external light source is brought to the portable device via an optical light guide.
Accordingly, the present invention provides a portable device having a plurality of selectable display modes for providing an image to a viewer, the portable device comprising:
an image source;
an illuminating light source for providing illuminating light to the image source for providing output light from the image source;
a first optical arrangement for forming the image from the output light along an optical path of the first optical arrangement; and
a second optical arrangement, disposed in the optical path, for modifying the image forming of the first optical arrangement.
According to the present invention, the selectable display modes include:
a first mode for allowing the viewer to perceive the image by placing an eye in the optical path adjacent to the portable device;
a second mode for allowing the viewer to perceive the image formed on a surface disposed in the optical path adjacent to the portable device;
a third mode for allowing the viewer to perceive the image by placing the eye in the optical path at a distance from the portable device; and
a fourth mode for allowing the viewer to perceive the image formed on a surface disposed in the optical path at a distance to the portable device.
The present invention will become apparent upon reading the description taken in conjunction with FIGS. 1 to 7.